* 
134 R. D. Irving—Hornblende of the Northwestern States. 
which so far as [ know he was the first to do, that all of the 
inally the same in origin, structure, composition and name,— 
basalt.”” In his view that these ancient greenstones were once 
“basalt,” Mr. Wadsworth is not wholly peculiar, since the same 
generalization has been extended by others as well as by hin 
over all ancient hornblendic eruptive rocks,” while the “ dio- 
rites” of many other regions have been shown to be merely 
altered augitic rocks.™ 
n 1880-81, I was engaged in a microscopic study of the 
rocks of the entire extent of the Keweenaw series, the results — 
of which study are given in a memoir forming vol. v of the 
monographic series of the publications of the U. 8. Geological 
Survey, and in an abstract of this memoir in the Third Annual 
the paper above alluded to was printed we have examined 
many more sections from the Archzean rocks, from Lake Huron 
to the Mississippi, and have thus far found nothing to change 
our views. 
22 p. 46. 
% e.g. Judd, “ Volcanoes,” 1881, pp. 261-268; see also Wadsworth, Bull. Mus. 
Comp. Zool., 1879, v, 275-287; Science, 1883, i, 127-130. ae 
% e.g. Belgium, see Geikie’s Text-Book of Geology, 1882, p. 143. See a 
Wadsworth, Proc. Bost. Soc. Nat. Hist., 1877, xix, 217-237. 
% pp. 618-622 2 Geol. of the Wis., vol. iv, pp. 625-714. 
